1. Field of Invention
This invention is in the field of moving target detection for use with radar imaging and/or target detection using a single channel receiver.
2. Description of the Related Art
Synthetic Aperture Radar (SAR) radar is used for ground mapping as well as target identification. The general principle behind SAR is to coherently combine the amplitude and phase information of radar returns from a plurality of sequentially transmitted pulses from a relatively small antenna on a moving platform.
The plurality of returns creating a SAR image generated by the transmitted pulses along a known path of the platform make up an array. During the array, amplitude as well as phase information returned from each of the pulses, for each of many range bins, is preserved. The SAR image is formed from the coherent combination of the amplitude and phase of return(s) within each range bin, motion compensated for spatial displacement of the moving platform during the acquisition of the returns for the duration of the array.
The plurality of pulses transmitted during a SAR array, when coherently combined and processed, result in image quality comparable to a longer antenna, corresponding approximately to the “length” traveled by the antenna during the array. Imaging in SAR depends on Doppler frequency bins. A moving target being imaged will experience a Doppler frequency shift, hence be possibly imaged in an inaccurate Doppler bin. Thus, where moving ground targets of interest are superimposed on stationary, non-moving clutter, imaging and locating of moving targets may be degraded because there is no definite correspondence between target angle and the Doppler shift of the target. Sometimes, resolving the uncertainty in position of a moving target with respect to the SAR map, requires more than one target measurement, presenting undesirable extended target acquisition time.